On July 28, 2025, about 0604 mountain daylight time, a Piper PA-22-150 airplane, N9642D, was substantially damaged when it was involved in an accident near New Underwood, South Dakota. The pilot was seriously injured and the passenger sustained fatal injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The airplane departed from the Kauer Private Airport (3SD2), Box Elder, South Dakota, for the local area flight. There were no known witnesses to the accident. A search revealed no automatic dependent surveillance-broadcast data for the accident flight. The airplane impacted a powerline along the perimeter of a pasture about 5 miles east-southeast of the departure airfield. The airplane ultimately impacted the pasture and came to rest inverted about 650 ft from the powerline. The initial ground scar was adjacent to a barbed wire enclosure and a wooden fence post on a heading of about 80°. The ground scar contained a fragment of wood and fabric from a wingtip bow along with fragments of red lens material from the left wingtip navigation light lens. Portions of powerlines were found along the debris field and entangled with the wreckage. The airplane sustained substantial damage to both wings, the fuselage, the vertical stabilizer, rudder, and elevator. Flight control cable continuity was confirmed from the cockpit to each of the flight control surfaces except for a separation in the aileron chain segment and the elevator pushrod. The Sensenich M74DM aluminum fixed pitch propeller was separated from the crankshaft propeller flange and located in the debris path near ground scars. The propeller exhibited chordwise polishing and bending. The aft face of one blade sustained gouges from impacting a powerline cable. The engine, a Lycoming O-320-A2A, was removed from the engine mounts and placed on an engine hoist. The engine crankshaft was rotated by hand via the crankshaft flange. Valve train movement was observed at all cylinders. Engine drivetrain continuity was confirmed. Thumb compression and suction were observed at all cylinders. Oil was expelled from one of the oil filter lines that was found compromised when the crankshaft was rotated by hand. The cylinders were borescope inspected, and no anomalies were noted. The fuel strainer bowl beneath the right front seat remained intact and the sump drain was actuated to produce liquid which was similar in both odor and color with automotive gasoline. The fuel strainer bowl on the firewall was impact damaged and separated from its mount. The firewall strainer screen was partially separated from its mount and was free from blockage. Fuel was collected and tested with water finding paste, with no water found in the sample. Both magnetos remained attached to the engine accessory case. The magnetos were removed and when rotated by hand, spark was observed from all the leads. No pre-impact anomalies were found with the airframe or engine that would have precluded normal operation. A handheld Garmin GPSMAP 496 unit was found within the wreckage and was sent to the NTSB Vehicle Recorders Laboratory. The sun’s position at the time of the accident was about 4° above the horizon on an azimuth of 67°.